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Test Code PTNFTM Phenytoin, Total and Free, Serum

Additional Codes

MAYO: PNTFT

EPIC: LAB176

Useful For

Monitoring for appropriate therapeutic concentration of both free and total phenytoin: free phenytoin level is the best indicator of adequate therapy in renal failure

Profile Information

Test ID Reporting Name Available Separately Always Performed
PNYF Phenytoin, Free, S Yes Yes
PNYA Phenytoin, Total, S Yes Yes

Method Name

PNYF: Membrane Separation/KIMS

PNYA: Kinetic interaction of Microparticles in a Solution (KIMS)

Reporting Name

Phenytoin, Total and Free, S

Specimen Type

Serum Red


Specimen Required


Container/Tube: Red top

Specimen Volume: 2 mL

Collection Instructions: Red-top tubes should be centrifuged and aliquoted within 2 hours of collection.


Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Red Refrigerated (preferred) 7 days
  Frozen  14 days
  Ambient  7 days

Reject Due To

Gross hemolysis Reject

Reference Values

Phenytoin, Total

Therapeutic: 10.0-20.0 mcg/mL

Critical value: ≥30.0 mcg/mL

 

Phenytoin, Free

Therapeutic: 1.0-2.0 mcg/mL

Critical value: ≥2.5 mcg/mL

Day(s) and Time(s) Performed

Monday through Sunday; Continuously

Performing Laboratory

Mayo Clinic Laboratories in Rochester

LOINC Code Information

Test ID Test Order Name Order LOINC Value
PNTFT Phenytoin, Total and Free, S 34540-5

 

Result ID Test Result Name Result LOINC Value
PNYF Phenytoin, Free, S 3969-3
PNYA Phenytoin, Total, S 3968-5

CPT Code Information

Phenytoin, total-80185

Phenytoin, free-80186

Forms

If not ordering electronically, complete, print, and send a Therapeutics Test Request (T831) with the specimen.

Test Classification

This test has been cleared, approved or is exempt by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.